Question

find the number of terms in following ap 12, 15 , 18....60​

Answer 1

Answer:

n=8

Step-by-step explanation:

ThegivenA.Pis21,18,15.....

so,

a=21

a+d=18

∴d=−3

now

a(nthterm)=a+(n−1)d

⇒0=a+(n−1)d

⇒0=21+(n−1)(−3)

⇒n−1=

−3

−21

⇒n−1=7

⇒n=7+1

∴n=8

Hence,therequiredtermis8.